350 won't start-where should I look?

[72C10chevy4x4]

it's a 78 350 w/ the coil built into the cap (is that an HEI?).

The engine will NOT start. replaced the inline fuel filter in the 2 barrell carb-tested it and there is plenty of gas coming out (pumped it manually and observed it squirting in). Air-tryed placing a towel over the carb, closing the butterfly shut, partially open, no indication it wants to start. finally, replaced cap,rotor and checked spark at end of a plug-it's there, but not strong. not sure how strong it should be, but there is spark. will go back and replace plugs to see if that helps.

how about the spark-how much spark do you NEED to start the engine? gas and starting fluid in the carb made no impact on it starting and I hooked up the jumper cables to get it turning more quickly-still no dice.

help! I've exhausted all my ideas except for a weak coil-would like to know it's bad before buying another (is there a test?)